1996 Mitsubishi Pajero DRIVE SHAFT BOOT BREAKING OFF

I took my Pajero to have the drive shaft serviced in order to get rid if a vibration at 2000 revs in 5th gear at +- 80km/h. Thereafter the boot that surrounds the CV joint on the drive shaft (on the end where it connects to the gear-box) have broken off three times over short distances. What can be the cause of the boot breaking off through explosion / tearing? Thanks. Kobus